Generally, a gas combustion type driving tool is provide with a cylindrical movable sleeve in an upper part of a cylinder, as described in patent documents 1 and 2. When the movable sleeve is closed so that a combustion chamber becomes in a tightly closed state, a combustible gas and a fresh air are supplied into an inside of the combustion chamber. After the combustible gas and the air are agitated and mixed by the rotation of a fan, a mixed gas is ignited and explosively burned. A high gas pressure acts on a piston to drive a fastener. After an end of a driving operation, the combustion chamber is opened to exhaust the combustion gas, whereby a next driving operation is prepared.
Patent document 1: JP-B-04-048589
Patent document 2: JP-A-2001-162560
The movable sleeve is disposed on an upper portion of the cylinder. By moving this movable sleeve upward or downward, the combustion chamber is opened and closed. That is, when the movable sleeve is moved upward, it comes into contact with an upper seal part and a lower seal part provided on an outer circumferential surface of a cylinder head provided above the cylinder and the outer circumferential surface at the upper end of the cylinder, so that the combustion chamber is placed in a tightly closed state, as described in patent documents 1 and 2. When the movable sleeve is moved downward, the seal with the upper and lower seal parts is released so that the combustion chamber is placed in an open state.
In this manner, in a structure in which the cylinder and the movable sleeve are disposed in series in a vertical direction, it is required a space for disposing the movable sleeve on an upper portion of the cylinder, and it is also required a space for moving the movable sleeve upward or downward on an upper side of the movable sleeve. Therefore, the total height of the driving tool is increased, thereby making a tool size larger.
However, the driving tool with great total height has a problem that the tool is not only heavy and tiring, but also less convenient during carrying out a corner driving operation or an oblique driving operation because the upper part is an obstacle.
On the contrary, if the height of the movable sleeve is reduced, the total height is reduced, but a volume of the combustion chamber is smaller to make the combustion energy smaller and a driving capability lower. Besides, though there is a possible solution for increasing the diameter of the movable sleeve to suppress the height of the combustion chamber, the body of the driving tool is thickened even though the total height can be suppressed, whereby the tool is difficult to handle and is unsuitable for carrying out the corner driving operation.